This invention relates to a down hole assembly used to clean tubular strings. More particularly, but not by way of limitation, this invention relates to an apparatus and method for cleaning the internal diameter of casing strings with a bristle brush circumferentially arranged about a down hole assembly.
In the development of oil and gas fields, operators will drill a well to a hydrocarbon reservoir, and thereafter, run a casing string through the production formation. The casing string will then be cemented into place. In turn, the well will then be completed as is well appreciated by those of ordinary skill in the art.
The optimization of production is an important criteria of any completion. Studies have shown that residue on the internal diameter of the casing string (such as cement, pipe dope, scale, burrs, etcetera) have a negative impact on productivity. Specialized completion fluids devoid of fines, solids and other debris are used to complete the well. Therefore, a major emphasis has been made to clean the inner diameter of the casing string.
Thus, when the operators have finished the pumping of a cement composition through the well casing, a work string is lowered on which a mechanical scraping device is used to scrap the walls of the casing. In the prior art, various types of casing scrapers are in use prior to displacement of a clean completion fluid. That is why it is so important to clean the casing wall as much as possible since it takes less time to ultimately filter the displaced completion fluids. Also, cleaning will eliminate foreign matter such as cement sheaths, scale, burrs and barite which in turn allows the tools used in the completion process to properly perform.
The scraping action of traditional scrapers with blades also have been known to leave a fine film of oil base or synthetic fluid residue on the casing wall. Prior art devices also cause problems because of the hardness of their blades cannot get into the casing connections as brushes can. Also, casing scrapers in high deviated holes collapse to the low side of the casing causing a great deal of wear on one side and the top side of the hole is not properly cleaning the high side due to ineffective engagement with the high side.
Therefore, there is a need for a down hole assembly that will be effective in cleaning a well bore that contains an oil base and/or synthetic fluid. There is also a need for a cleaning apparatus that will be effective in highly deviated wells. There is also a need for a down hole assembly that will have scraper brushes that are of sturdy construction and allow for ease of replacement.